Question: When did Frederick William, Elector of Brandenburg marry Countess Louise Henriette of Nassau?
Paraphrase: Frederick William, Elector of Brandenburg married Countess Louise Henriette of Nassus on which date?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q152727 p:P26 ?s . ?s ps:P26 wd:Q196301 . ?s pq:P580 ?value}